G'day gunamani,
Welcome to PPRRuNe!
A bit of both I reckon, the tyre wear limits should be in the ops manual for the aircraft type.
There is quite a range of allowable wear, cuts and other damage allowed on the type I fly, sometimes with a limit on the number of landings allowed or the requirement to be inspected after each landing.
For the other two respondents, I think you need to re-read gunamani's post again, carefully.
Regards,
BH.